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A*STAR Singapore - Nano-fabrication - Medical sensors improve with holey Gold nano-structures

DCN Corp® - Localized surface plasmon resonance (SPR - bright areas) around a Gold (Au) nano-hole enhances the fluorescence of a bio-marker dye (Y-shaped molecule) when a specific molecule of interest (purple circle) is present.  Credit - © 2013 A*STAR Institute of High Performance ComputingA new methodology which can fabricate gold nano-structures quickly and efficiently could enable for the creation of highly sensitive and portable medical sensors

Continual advances in nanotechnology are ensuring to provide new concepts for medical imaging and sensing.  In particular, Gold (Au) nano-structures can efficiently enhance the fluorescence of marker dyes, which are typically employed to detect bio-molecules and diagnose specific diseases.

In new research by Ping Bai at the A*STAR Institute of High Performance Computing, Singapore, and co-workers they have developed a fast and inexpensive methodology to fabricate arrays of Au nano-holes. [1]  The researchers had demonstrated a new sensor chip - built employing nano-structures which can accurately detect cancer-related molecules in blood, but still small enough to be employed in portable medical devices.  Essentially nano-hole arrays are designed whereby incident light of certain wavelengths will induce large-scale oscillations of the internal Au electrons - known as localised surface plasmon resonance (SPR).  The localised SPR focuses the absorbed light energy to enhance fluorescence (see image above).

As stated by Bai - "Commercial SPR systems are already used in hospital laboratories, but they are bulky and expensive," - "We would like to develop small, hand-held devices for on-the-spot clinical use.  This requires localised SPR, for which we need nano-hole arrays."

Previously, nano-hole arrays have been fabricated by employing electron-beam lithography (EBL), which is both expensive and time consuming.  Bai and co-workers used EBL to create a Nickel (Ni) mold and then used the mold to print nano-hole patterns onto a photo resist material.  The researchers fabricated the nano-structures by evaporating Au onto the patterned structure before peeling-off the photo-resist material.  Since the Ni mold can be reused on many occasions - such a methodology - known as nano-imprinting - can produce large numbers of Au nano-hole arrays.

Bai continues to state - "We fabricated arrays of 140 nanometer-square nano-holes with very few defects,"  As a first demonstration, the researchers demonstrated that a sensor chip made with their nano-hole arrays could detect prostate cancer anti-gen in blood, which is ten times more sensitive than an identical device that used a Au film without nano-holes.  Smartly optimising the chip/sensor design would further improve the bio-sensitivity, Bai notes.

The team believes that these chips could be incorporated into cheap and portable Point-of-Care (PoC) devices for rapid diagnosis of diseases such as dengue fever.  As concluded by Bai - "The micro-fluidic cartridge built using our nano-hole arrays is about the size of a credit card" - and - "In the future, we hope to build detectors that use very simple light sources, such as LEDs, and simple detectors similar to smartphone cameras.  These devices will have widespread applications across medical science and could even be used to detect contaminants in food, water or the air."  Original article available here

The A*STAR Singapore claims, as stated above could be strongly counter-acted by DCN Corp, whereby it is clear the company can provide a competing nano-fabrication methodology with a much faster and inexpensive SPR turnaround.  Especially in regard of the number of steps to acquire the same SPR chip/sensor quality.  Therefore, being able to competitively supersede - if you and/or your colleagues are interested in making the above research claims reality - please ensure to contact the company as soon as practicably possible.

[1] Wong, T.I., Han, S., Wu, L., Wang, Y., Deng, J., Tan, C.Y.L., Bai, P., Loke, Y.C., Yang, X.D., Tse, M.S., Nq, S.H. and Zhou, X. High throughput and high yield nano-fabrication of precisely designed gold nano-hole arrays for fluorescence enhanced detection of bio-markers. Lab on a Chip 13, 2405-13 (2013) Journal citation available here